1. Atomic Theory 1

2. What Happens in Vegas stays in Vegas

3. Atomic Theory Theories in science are proposed to explain the evidence available at the time. As new evidence is discovered theories are adapted to explain new data. This is the nature of Science. In the future this will continue.

4. Democritus Plato 460-370 BC Atoms make up the world

5. Aristotle Plato 384-322 BC Four Elements Teacher of Aristotle

6. Aristotle Wind Fire Water Earth dryness wetness coldnesshotness conflictharmony The Four Element Theory PropertiesForces

7. The Four Element Theory lasted for about 2 thousand years because no one tested the theory with scientific experiments. It was not a scientific theory- which is tested by experiment.

8. John Dalton 1766-1844 Atomic Theory

9. Dalton’s Atomic Theory- 1808 Evidence 1. The Law of Conservation of Mass 2.The Law of Constant Composition- water is 11 % H and 89 % O Theory 1. Each atom is an indestructible and unique spherical particle 2.Atoms combine in simple whole number ratios to form compounds

10. Hydrogen Oxygen Lithium

11. Dalton Theory- Water 1 g H 16 g O 18g O

12. 16 g O 1 g H Dalton Theory- Water 18g O

13. = 11% H 16 g O 1 g H Dalton Theory- Water 2 g H 18 g H 2 O x 100%89 % O

14. Still 11 % H 89 % O Having a molecule (atoms combine in simple whole # ratios) explains the law of constant composition. No matter how much water you have its still 11% H

15. 2H 2 + O 2  2H 2 O If the atoms are not destroyed then the mass does not change

16. J. J. Thomson 1871-1937

17. The Thomson Theory of the Atom Evidence 1. The electrical nature of matter beta particles static electricity current electricity Theory 1.The atom is made up of positive material with negative particles throughout- like blueberries in a blueberry muffin.

18. ++- +-+ + -+- + -+- + -++- + +-+- + - + - + + - The Thomson Atom 1903

19. Ernest Rutherford 1871-1937

20. The Rutherford Atom 1911 Simulation Evidence: Gold Foil Experiment 1.99.99 % of alphas are not deflected 2.0.01 % of alphas are radically deflected Theory 1.Most of the atom is empty space. 2.There is a small dense nucleus in the center of the atom that makes up most of the mass. Electrons circle the nucleus randomly.

21. The Rutherford Atom 1911 Scale: nucleus is home plate; atom is the baseball field Be - - - - Nucleus- 4 protons and 5 neutrons Electrons Nucleus- is small but has most of the mass

22. Cornelis Escher 1898-1972 Discovery of the Nucleus Size of the Atom